package chapter09_1;


import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

import java.util.HashMap;
import java.util.Map;

/**
 * RSA安全编码组件
 * 
 * @author 梁栋
 * @version 1.0
 */
public abstract class RSACoder {
	
	/**
	 * 数字签名
	 * 密钥算法
	 */
	public static final String KEY_ALGORITHM = "RSA";

	/**
	 * 数字签名
	 * 签名/验证算法
	 */
	public static final String SIGNATURE_ALGORITHM = "SHA1withRSA";

	/**
	 * 公钥
	 */
	private static final String PUBLIC_KEY = "RSAPublicKey";

	/**
	 * 私钥
	 */
	private static final String PRIVATE_KEY = "RSAPrivateKey";

	/**
	 * RSA密钥长度 默认1024位，
	 *  密钥长度必须是64的倍数， 
	 *  范围在512至65536位之间。
	 */
	private static final int KEY_SIZE = 512;

	/**
	 * 签名
	 * 
	 * @param data
	 *            待签名数据
	 * @param privateKey
	 *            私钥
	 * @return byte[] 数字签名
	 * @throws Exception
	 */
	public static byte[] sign(byte[] data, byte[] privateKey) throws Exception {

		// 转换私钥材料
		PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(privateKey);

		// 实例化密钥工厂
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);

		// 取私钥匙对象
		PrivateKey priKey = keyFactory.generatePrivate(pkcs8KeySpec);

		// 实例化Signature
		Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);

		// 初始化Signature
		signature.initSign(priKey);

		// 更新
		signature.update(data);

		// 签名
		return signature.sign();
	}

	/**
	 * 校验
	 * 
	 * @param data
	 *            待校验数据
	 * @param publicKey
	 *            公钥
	 * @param sign
	 *            数字签名
	 * 
	 * @return boolean 校验成功返回true 失败返回false
	 * @throws Exception
	 * 
	 */
	public static boolean verify(byte[] data, byte[] publicKey, byte[] sign)
			throws Exception {

		// 转换公钥材料
		X509EncodedKeySpec keySpec = new X509EncodedKeySpec(publicKey);

		// 实例化密钥工厂
		KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);

		// 生成公钥
		PublicKey pubKey = keyFactory.generatePublic(keySpec);

		// 实例化Signature
		Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);

		// 初始化Signature
		signature.initVerify(pubKey);

		// 更新
		signature.update(data);

		// 验证
		return signature.verify(sign);
	}

	/**
	 * 取得私钥
	 * 
	 * @param keyMap
	 * @return
	 * @throws Exception
	 */
	public static byte[] getPrivateKey(Map<String, Object> keyMap)
			throws Exception {

		Key key = (Key) keyMap.get(PRIVATE_KEY);

		return key.getEncoded();
	}

	/**
	 * 取得公钥
	 * 
	 * @param keyMap
	 * @return
	 * @throws Exception
	 */
	public static byte[] getPublicKey(Map<String, Object> keyMap)
			throws Exception {

		Key key = (Key) keyMap.get(PUBLIC_KEY);

		return key.getEncoded();
	}

	/**
	 * 初始化密钥
	 * 
	 * @return Map 密钥对儿 Map
	 * @throws Exception
	 */
	public static Map<String, Object> initKey() throws Exception {

		// 实例化密钥对儿生成器
		KeyPairGenerator keyPairGen = KeyPairGenerator
				.getInstance(KEY_ALGORITHM);

		// 初始化密钥对儿生成器
		keyPairGen.initialize(KEY_SIZE);

		// 生成密钥对儿
		KeyPair keyPair = keyPairGen.generateKeyPair();

		// 公钥
		RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();

		// 私钥
		RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();

		// 封装密钥
		Map<String, Object> keyMap = new HashMap<String, Object>(2);

		keyMap.put(PUBLIC_KEY, publicKey);
		keyMap.put(PRIVATE_KEY, privateKey);

		return keyMap;
	}
}
